cardreader.js

var spawn = require('child_process').spawn;
var util = require('util');
var EventEmitter = require('events').EventEmitter;

function CardReader() {
  
  var reader;

  var lastUID = "";
  var me = this;
  function spawnReader() {
    reader = spawn('python', ['uidgrabber.py']);
    console.log("uidgrabber running pid: " + reader.pid);
  }

  function handleExit(reader) {
    reader.on('exit', function (code) {
      console.log('uidgrabber process exited with code ' + code);
      me.emit('exit', code);
      spawnReader();
      handleExit(reader);
    });
  }
  spawnReader();
  handleExit(reader);

  // Handle stuff.
  
  reader.stderr.on('data', function (data) {
    console.log('stderr: ' + data);
    me.emit('error', data);
  });
  
  reader.stdout.on('data', function (data) {

    var data = data.toString();
    data = data.replace(/\u001b\[\d{0,2}m/g, ''); // Remove ANSI colors.
    var uid = /UID: (.+)/.exec(data);

    if (uid) {
      uid = uid[1];
      if (uid != lastUID)  {
        // This is not the last card we read, so lets emit it.
        me.emit('cardRead', uid);
      }
      lastUID = uid;
    }
  });
}

util.inherits(CardReader, EventEmitter);
exports.createReader = function () {
  return new CardReader();
}